The present invention relates to an improved method for compensating changes in an array antenna radiation pattern due to faulty elements by using remaining elements in the array for compensating the change resulting from the failing elements.
Large array antennas do have a rather high probability that a fault may occur in one or more of the antenna array elements. If such faults are of the character that certain antenna elements get a reduced or no radiation functionality, fundamental antenna performances, e.g. side lobe levels, are strongly deteriorated.
Instead of hardware repair of the damage, by replacing failing parts, a software solution adjusting amplitude and eventually the phase of the remaining antenna elements may take place for at least partly repairing the damage.
There are found several scientific reports considering this field of techniques. Certain of these references are based on a re-optimization of amplitude and phase for the remaining antenna elements, while others are based on methods within the signal processing to recreate the signals of the failing antenna elements. A number of representative articles are listed below in the last paragraph before the disclosed present claimed improved method.
An U.S. Pat. No. 5,416,489 to Mailloux 1995 describes a procedure and an apparatus for phased array error correction. Mailloux discloses a technique that enables array error correction by replacing the signals from failed elements with processed signals derived from operating elements. However, the technique according to Mailloux assumes that it is already known in which directions the antenna radiation pattern has to be improved. The approach of Mailloux will result in that some of the remaining angles may experience an even more deteriorated performance.
Therefore there has been a demand of further improving the techniques for compensating losses in an array antenna radiation pattern due to faulty elements.
A method and a system for compensating for failed elements in an antenna array are disclosed. The method assumes that at least the amplitude and, in most cases, the phase of, at least, some of the individual elements can be controlled to some extent.
If one or more of the antenna array radiating elements are failed, at least some remaining elements are used to correct for this. The amplitude and phase radiation pattern of one of the failed elements is then synthesized using K of the remaining elements. The resulting excitation from this synthesis is superimposed on the failed array excitation at the positions of the K remaining elements. This procedure can be repeated for all the failed elements using the principle of superposition.
According to the present method, by positioning a phase reference point of the array antenna in a failed element a unity value for all angles may be synthesized by means of the calculation means. K neighboring elements in the array are selected and weighted with a specific excitation, exofailed, of a failed element, for compensating the erroneous antenna radiation pattern. This results in a steering angle independent compensation as a total control vector consists of a sum of a constant compensation vector and an initial control vector.
A system utilizing the method uses a control unit, which comprises a calculation means and the control unit, via a control signal network, controls a T/R-module for each element of the array, whereby the control unit sets the phase and amplitude of each element in the array.
The method is set forth by the independent claim 1 and a further embodiment of the method is set forth by the dependent claim 2.
A system utilizing the present method is set forth by the independent claim 3 and the dependent claim 4-5.